sethleigh
I'm using the Monoprice 28" Crystal Pro 4K monitor, which I picked up on sale over Memorial Day for around $348.
 
Other than the reflections off its mirror-like glass screen when the room behind me is well lit, it's an astoundingly beautiful monitor. I had never given Monoprice much thought, thinking it was just a purveyor of cheap Chinese crap, but my brother told me he has two Monoprice monitors and they're great (he has one each of the two 28" 4K monitor models from Monoprice), so I took his word on it and bought it. 

I'm more than well pleased. It's 60hz with a DP 1.2 cable, and looks great. I'm so spoiled by 4K now that I can't stand looking at 1080p monitors anymore. One of my work machines has a nice new cheap Lenovo 24" 1080p monitor that I thought was perfectly fine. Until I got the 4K that is. Now I can't stand looking at the Lenovo. 4K will totally wreck you for any lower resolution.

It will also wreck your wallet. My Geforce 960 SSC 4gb was doing just fine with my 1920x1200 monitor, but it fell over hard when ordered to support my new 4K monitor, and I knew I had to have an upgrade. I first intended to buy a 1070, but after looking at the benchmarks and reviews I realized a 1070 wouldn't be enough for 4K, and I was right. While most games prior to the current generation will peg my fps at 60 with high quality settings, things like The Division require usually medium settings, and some things like shadows have to be cranked down to Low in order to keep my framerate up around 60, and that's with a 1080 SC overclocked to +100/+350 and my Xeon 5680 running at 4.1ghz.

XeqtR_GTR
PG279Q, best 1440p panel you can buy today.

hapkiman
#2 is a Dell P2715Q 27" IPS 3840x2160 UHD @60Hz - I have it set to 6ms response (GTG) and it looks glorious.  No lag or ghosting at all!
 

xizorgetspeed
Of course now that I plug in my 4K display I'm noticing the lack of smoothness. (groans)

hehehippie

xizorgetspeed
Of course now that I plug in my 4K display I'm noticing the lack of smoothness. (groans)

lol it's just give or take right now with 3440x1440 vs 4k.
 
for me, 3440x1440 is a better choice because it has alot more pro's than a 4k monitor. the only thing that 4k has over it is a bit of sharpness. i'm a gamer, so that's kind of a moot point for me.
 
i won't even consider 4k until 1 or 2 more generations of hardware because of the lower refresh rates and price of OLED. IF i jump to 4k, it'll have to be a bigger size (around 35"-40") to replace the immersive feeling that 21:9 has given me. that'll be friggin groovy if they made a 21:9 4k monitor.

Balubish
Check the hz then, sounds like 30hz

FattysGoneWild

FancyPilot

Beasthunt
I have the Dell s2716dg, it's a fantastic monitor. I think it's on sale right now as well. Gsync, 144hz, ulmb and all that jazz.

I too have the Dell Gaming S2716DG. Its a 1440p 144hz 1ms G-sync monitor that is amazing and no quality issues like Asus or Acer. Dell is #1 in monitors for a reason. You just have to get a gaming one! Highly, highly recommend this monitor.

 
I can vouch for this monitor. You wont find any thing better for $449 right now. BUT. They do have QC issues. No where near like Asus/Acer though. I received 2 brand new Dell's that was bad. One had a dead pixel right in the middle of the screen. The other brand new replacement had some kind of dirt/smudge physically underneath the screen. I am going on my 3rd replacement. I am working with Dell directly this time. They are sending me a brand new replacement through dell.com The other 2 came from BestBuy.com That should tell you how much I liked the monitor and willing to go the length for a good working one. Bestbuy has been a rock star during this whole process. Zero complaints with them. Dell just needs to improve QC a little bit more. 
 
Sorry OP. Just looked and it is now sold out at the $449 price. They did not last long.